Paint and varnish remover containing activated acetone



Patented Oct. 25, i932 UNirEn BORIS N. LOUGOVOY, OF MONTCLAIR, NEW JERSEY, ASSIGNQR T09 CHADELQID CHEMEGAIQ:

COMPANY, OF ."NEW' YORK, N. Y., A CORPORATION OF WEST VIRGINIA. i

. O PAINT AND VARNISH REMOVER CONTAINING ACTIVATED ACE'IONE No Drawing. Application filed June 29,

. tone carrying three or four ounces of para-fiin wax per gallon, with various modifications and additions.

The activity of a paint and varnish remoyer is usually tested in the trade by a methodv which is not absolutely reliable but nevertheless is regarded sufiiciently convincing to the user. This method involves the application of some of the removing composition to a surface coated with a paint or varnish and noting the time taken for the surface to wrinkle. This wrinkling efl'ect is regarded as an indication of the solvent action or cutting power of the removing composition, activity being in inverse ratio to the time required.

Hence the methodadopted in conducting the tests carried out in connection with the development of the-present invention was as follows: A piece of old painted wood was selected, taking care that the portion used had a good even, thick coat of paint. This was cut into strips. Various solvents were placed in a seriesof test tubes and a strip of the painted wood was put into each test tube. The time which elapsed before the first appearance of any wrinkling was noted accurately for each solvent by means of a stop Watch. The comparative removing action was thus roughly represented by the number of seconds. n

Solvent mixtures vary greatly in cutting power. In removers involving the use of a.

penetrating hydrocarbon, such as benzol, and a loosening solvent of an alcoholic or ketonic nature, a very great variation is observable in the cutting action depending upon the choice of solvents. Practically speaking, benzol is the most active and cheapest penetrating hydrocarbon. Acetone is probably the Inost'readily available and highly effective ketone body which is' being used in paint and varnish removers as a loosening solvent at the present time.

In the course of investigations the field 1928. Serial No. 289,32tt.

of paint and varnish removers, I discovered that a product obtained from acetone by trea ment with a small amount of alkali would produce a substantial increase in cutting pow= painted strips of the kind described above:

Table. 1

' Cuttl Single solvents" power secon ds B an 101 Chlorooenzol. 288 Anhydrous methyl alcohol 24 Anhydrous ethyl alcohol 1020 Isopropyl alcohol (98%) 2400 Diacetone alcohol 403 Acetone 80 Activated-acetone (as described below). 75 Methyl ethyl lm 75 Mesityl oxide 210 Furfural 300 Ethyl nnnfnh: BINARY MIXTURES (EQUAL PARTS) Benzol-anhydrous methyl alcohol Benzol-anhydrous ethyl alcohol- TERNARY MIXTURES (IN EQUAL PARTS) Benzol-anhydrous methyl alcohol-acetone Benzol-anhydrons methyl alcohol-"activated acetone. Benzol-anhydrous methyl alcohol-methyl ethyl ketone Benzol-acetone-ethyl alcohol Benzol activated-acetone-methy1 acetate As stated, the main feature of the present essee sssaaaassesasssase invention is the use of a product obtainable by activating acetone. This product contains a mixture of various ketone condensation products together with unconverted acetone.

When acetone is subjected to the action of a small amount of an alkali metal hydroxide, a portion of the acetone undergoes intermolecular condensation to form a number of products of higher molecular weight among which mesityl oxide, diacetone alcohol, phoron and iso-phoron are mentioned.

I shall now illustrate the preparation of the activated acetone of the present specification.

'To prepare this product, commercial acetone, preferably in pure form, is treated with an alkaline substance capable of causing condensation, forming a certain proportion of products of higher boiling point. Alkaline condensating agents are, for example, quicklime, calcium hydroxide, barium hydroxide and similar alkaline earth metal hydroxides,

' and the like, which are substantially insoluble in acetone.

Sodium or potassium hydroxide can also be employed. The last two hydroxides are preferable and should be used in minute amounts (e. g., about 0.3%, more or less) and preferably in such pro ortions as will dissolve practically comp etely in the acetone. The acetone when exposed to a condensation agent of this character, or mixtures of such condensation agents, is permitted to undergo a reaction involving condensation, the treatment preferably being carried out at about room temperature for a period of a day or so, suflicient to bring about a substantial equilibrium between unchanged acetone and the higher boiling substances which are engen dered. The acetone mixture is then preferably neutralized. When neutralizing the product it is desirable to avoid an excess of acid and therefore it is better (although not necessary in all cases) to keep the product near the point of neutrality approximating the iso-electric point. Various organic and inorganic acids may be used for the neutralization and the employment of ases containing carbon dioxide to form car onates or bicarbonates are also not precluded. In some cases I may usethe alkali treated but unneutralized acetone directly in remover compo-1 sitions.

In connection with the neutralization it should be pointed out that when using the" above product in the present invention, it is usually desirable to avoid the presence of any unnecessary dissolved solids of a seemingly inert character, because such substances pres ent in the solvents used for paint and varnish remover usually tend to decrease the cutting power or speed) of the solvent. For this reason, ifand when neutralizing the alkalitreated acetone, it is advisable to use certain acids which form salts insoluble in acetone and in mixtures of acetone and other solvents used 1n palnt and varnlsh removers. Tartaric acid was found to be one of the mostsatisfactory for the purpose.

' After suflicient time for the-reaction has elapsed, the alkali-treated acetone generally is neutralized with an acid and the resulting salti,i if precipitated, may be separated either y in some cases, this precipitate may be allowed to remain in the composition. The product so obtained frequently will contain about of unconverted acetone and about 25% of higher boiling liquids. The mixture of those several substances, thus readily and conveniently obtained, constitutes the preferred composite solvent or activated-acetone of the present invention. The term activated-acetone is used throughout this specification and the appended claims to cover this alkali-treated and neutralized product. The high solvent power of this activated-acetone can be seen from Table 1. I may also use various fractions of the foregoing containing mixtures of solvents obtained by condensation.

In connection with the above described method of preparation of activated-acetone, it should be pointed out that acetone may occur both as normal or ketonic acetone and also as iso-acetone or enolic acetone. Enolic acetone has a structure corresponding to that of unsaturated alcohol (hydroxy pro ylene).

nolization apparently plays an important part in the condensation of acetone to form the higher boiling acetone derivatives. When acetone is treated with a small amount of alkali, such as potassium hydroxide to form a higher boiling derivative thereof, under most advantageous conditions about one-eighth of its volume of diacetone alcohol will be formed with simultaneous formation of about another one-eighth of its volume of products boiling between 60 (1., and C. In one treatment of acetone with alkali, an equilibrium is reached in which one-fourth (or even slightly more) of acetone will undergo condensation, with about three-fourths remaining unreacted.

I have found that this unreacted acetone, when recovered from one alkali treatment or distillation and when again subjected to the samealkali treatment, is much less reactive than the fresh previously untreated acetone. This I regard as largerly due to a lower enolic content and therefore it appears that enolic acetone and not ketonic acetone is the actual substance which will combine with itself (by a condensation reaction) to form these higher boiling derivatives. The reactivity of commercial acetone derived from various sources differs somewhat, which may ltering the liquid or by recantation. Or,

'. or unneutralized state gave results which be ascribed to some variation in the enolic content.

I have recorded in a copending application that certain substances may be added to acetone-alkali reaction mixtures which act as promoters of enolization, and which in consequence increase the yield of condensation products and bring about their formation in less time than would otherwise occur.

Such are substances containing the COH group, i. e.', such materials as tertiary alcohols andaldehydes-particulafly formaldehyde, are especially suitable as promoters. By the use of such promoters the yield of activated acetone can be increased to about 44% by weight of acetone taken.

The activated acetone used in most of the examples given in the present specification was made from a commercial'grade of acetone by treatment with small amount (.03%) of potassium hydroxide in presence of 2% of formaldehyde solution, allowing to stand for one day, finally neutralizing the products of reaction with tartaric acid, settling and filtering.

Referring to Table 1 representing the cutting power of various solvents, it should be 1 noted that activated acetone as compared with other ketone solvents, such as acetone, Y

methyl ethyl ketone, me'sityl oxide, and diacetone alcohol, is the stronger and more active solvent. 4 The same observation is truefor various mixtures of activated acetone with other solvents including hydrocarbons of the benzenoid type such as benzol and those of the non-benzenoid type such petroleum naphtha.

From the same table it should also be noted that while activated acetone maycontain mesityl oxide and diacetone alcohol, it is apparently not the presence of these two substances which produces the effect of the higher elficiency because a mixture of acetone with diacetone alcohol and acetone with mesityl oxide gave a cutting rate much slower than the rate for activated acetone itself.

l'herefore the potency of activated acetone cannot be credited to the primary condensation products individually considered, but

rather to the joint or co-operative effect of various acetone condensation products fromed simultaneously in the course of reaction.

It was also observed that an alkaline reaction does not favor but rather depresses the solvent power of activated-acetone-in removing compositions. Activated acetone prepared, as already mentioned, by using caustic alkalies and empolyed in the alkaline are illustrated in Table 2. The table gives the cutting power in seconds as measured on the same type wooden strips and by the same method as previously described.

It is also within the scope of this invenactivated acetone, preferably after a careful filtrat1on. v

' Table 2 Activated acetone Composition of solvent mix- Acetum used in each test 8mm) 1 Sampf 2 Samp 3 tone Alli. Neu. Alk. Neu. Alk. Neu.

Single solvents 90 60 75 60 70 55 80 Binary mixtures of above solvents with: Benzol 7O 60 45 55 45 65 Petroleum naphtha 200 125 200 130 200 130 280 Anhydrous methanol 30 50 40 45 35 45 Ternary mixtures of above solvents and two other solvents: Benzol-methylacetateL... .30 20 40 30 40 .25 Banzai-anhydrous methanol r 4. s0 40 40 '55 40 5o Petroleum naphth'a- 4 meth aceta 35 60 35 55 40 Samples 1, 2 and 3, mentioned in table above were made from acetone using different alkaline catalysts for the reaction. thousand cc. of acetone was used in each case to I Ordinarily however, I do not dis- One with one gram of potassium hydroxide; in

sample 2 with one gram of quicklime (calcium oxide) and in sample 3 with one gram of barium hydroxide. It can be seen from the above table that the neutralized prod not is of especial value, the alkaline product giving in all cases a slightly slower rate of attack.

Having described the preparation and the finish loosening" properties of ketone condensation solvents, which are the main features of the present invention, 1 will now give examples of the various paint and varnish removers madewith the above materials. It is understood that all formulas given below should be regarded only as examples and that it do not wish to restrict myself to the exact proportions and components given in'these formulas. All these examples will include in the formulas a wax, e. g., paraflin wax, as an agent to retard evaporation of the'solvents and in some cases will also include nitrocellulose (scrap celluloid) as an agent to increase theconsistency of the paint and varnish remover. It should be noted in this connection that the addition of various solids which are capable of dissolving in one of the solvents used in paint and varnish remover and to some extent carried into solution in the mixedsolvent forming the remover, gen erally will result in cutting down of the speed of a given solvent or of a mixture -of wax-containing compositions will be slower than the cutting speed of a corresponding mixture without a wax, for example: the introductionof 1% of nitrocellulose of second viscosity into acetone produced the following change in cutting speed as measured by the method described at the beginning of this application:

Pure acetone 80 seconds Acetone containing 1% of nitro- 130 seconds 62.5% retardation.

cellulose.

All removers made according to the formulas of the examples below were tested in the same manner on the same kind of painted surfaces, in order to obtain comparative figures. Each remover was placed on that surface in approximately the same quantity and the time was noted by means of a stop watch when the blistering or wrinkling of the surface was plainly observable. The cutting power was expressed in the number of seconds which elapsed before the appearance of such wrinkling. The proportion of ingredients is given by volume, including .wax, (which was measured in the melted state).

The examples are all arranged in the form of a table (Table 3) giving compositions of removers as well as the cutting speed both for these removers and for a corresponding remover containing acetone in place of acti vated acetone in each case:

TABLE 3.Ea'amples of paint and varnish remover compositions containing activated acetone Example Nos.

Solvents BenzoL. Petroleum nanhfhn ing remover containing nonactivatedaoetonel'n seconds 547 125 165 110 120 125 These results are surprising since heavier solvents usually retard cuttin action. Hence the formation of various higher-boiling sol vents from acetone would be expected to reduce instead of increase the activity thereof.

The employment of activated acetone in paint and varnish removers thus is .con-

Activated acetone may be distilled to remove a part of the free acetone and the solvent of reduced acetone content thus obtained may be used in making paint and varnish removers. In this way I obtain a finish renlover comprising activated-acetone containing free acetone present in a proportion less than that represented by the equilibrium point of alkaline condensation.

What I claim is:

1. A finish remover containing activatedacetone as a constituent thereof.

2. A finish remover containing activatedacetone and wax and a wax solvent.

3. A finish remover containing activatedacetone and methyl acetate, as wax precipitants.

4. A finish remover containing wax, a wax solvent selected from the herein described group consisting of benzol, trichlorethylene and monochlorbenzol, and containing activated-acetone and other wax precipitants selected from the herein described group consisting of methanol and methyl acetate, such remover being faster than a similar remover having the same composition but with ordinary acetone instead of the activatedacetone.

In testimony whereof I atfix my signature.

BORIS N. LoU'covoY. 

